Cooled ultrasonic transducer

ABSTRACT

An ultrasonic transducer comprises a back body, a front body, one or more piezo electric crystal discs sandwiched therebetween, and a central bolt holding the elements together. Cooling air passes into a central bore in the bolt, out the bottom of the bolt, and up through a longitudinal groove in the outside of the bolt to an annulus between the bolt and the piezo electric discs. The air then passes outwardly through radial grooves between the crystal discs and adjoining metal elements.

United States Patent lnventor Charles W. Pierson Rochester, N.Y.

Appl. No. 865,576

Filed Oct. 13, 1969 Patented Jan. 12, 1971 Assignee Eastman KodakCompany Rochester, N.Y.

a corporation of New Jersey COOLED ULTRASONIC TRANSDUCER 7 Claims, 4Drawing Figs.

U.S. Cl 310/8.9,

310/83 1nt.Cl H01v 7/00 Field ofSearch 310/89,

[56] References Cited UNITED STATES PATENTS 3,218,488 11/1965 Jacke310/82 3,283,182 11/1966 Jones et a1. 310/87 2,831,295 4/1958 Weiss310/8.2X

Primary ExaminerMilton O. l-lirshfield Assistant Examiner-B. A. ReynoldsAttorneys-Walter O, Hodsdon and Henry M. Chapin ABSTRACT: An ultrasonictransducer comprises a back body, a front body, one or more piezoelectric crystal discs sandwiched therebetween, and a central boltholding the elements together. Cooling air passes into a central bore inthe bolt, out the bottom of the bolt, and up through a longitudinalgroove in the outside of the bolt to an annulus between the bolt and thepiezo electric discs. The air then passes outwardly through radialgrooves between the crystal discs and adjoining metal elements.

PATENTEDJAMIQYI 3555297 FIG.

CHARLES 'w. p/mso/v BYg E VENTOR. 7

ATTORNEYS COOLED ULTRASONKC TRANSDUCER BACKGROUND OF THE lNVENTlON 1.Field of the invention The present invention relates to a novelultrasonic transducer construction having provision for improved coolingof the vibration producing elements.

2. @escription of the Prior Art Ultrasonic transducers have been wellknown for a number of years and have found extensive applications inindustry for the welding of plastics and other applications. The mostcommonly used ultrasonic transducers depend upon piezo electric crystalsfor generating the desired vibrations when oscillating electricalcurrents are applied thereto. An example of such an ultrasonictransducer is described in U.S. Pat. No. 3,328,610. When transducers areused continuously, the crystals tend to become quite hot and it has beenfound necessary to cool them as by passing a flow of air around theoutside of the transducer. While this is effective, l have found thatsubstantial heat still tends to build up in the crystals and theefficiency of cooling should be improved if possible.

SUMMARY OF THE lNVENTlON in accordance with the present invention theefficiency of cooling an ultrasonic transducer is improved by providingfor the flow of cooling fluid such as air through the center of thetransducer and then laterally outward in contact with the faces of thecrystals. This mode of cooling can be accomplished in a transducerhaving only a single piezo electric crystal but since the more commonlyused transducers employ two stacked crystals, the invention will bedescribed hereinafter with reference to such a transducer.

THE DRAWINGS in the drawings H6. 1 is a vertical sectional view, partsbeing in elevation showing an ultrasonic transducer in accordance withthe invention:

HG. Z is a cross-sectional sectional view taken along the line 2-2 inEEG. l;

HQ. 3 is a cross-sectional view taken along the lines 3-3 or 3-3\ inFIG. 1; and

HG. 4 is a cross-sectional view taken along the line 4-4l in l-"lG. ll.

THE PREFERRED EMBODRMENT Referring to the drawings there is shown anultrasonic transducer 'l comprising a metal back body l l, a metal frontbody 13 and a piezo electric crystal means (I sandwiched between and incontact with end faces l5 and R7 of such bodies.

A central bolt l9 extends through bores in the bodies ll and 113 and inthe crystal means C and is threaded at its lower end into the bore 21and in front body 713. The head of bolt l9 bears against the top of backbody ill to hold the elements tightly together.

The crystal means C comprises upper and lower piezo electric crystaldiscs 23 and 25 and an intermediate metal spacer 27 having oppositefaces in intimate contact with the faces of the crystal discs, all threebeing spaced from bolt 19 so that no electrical contact is made with thebolt. insulation from the bolt can also be assured by positioning acylindrical insulator within the annular space 33, with a sufficientlyloose fit to per mit the flow of air. Discs 23 and 25 can be any desiredpiezo electric crystal material but the well-known PZT crystal (lead, ziconate, titanate) is preferred.

For cooling the transducer, the bolt 19 is provided with a longitudinalcentral bore 29 whose upper end is in communication with an air supplyconduit 31, and whose lower end opens into the bottom of bore Zll. Theexternal surface of bolt i9 is provided with a longitudinal groove 3 11which extends from the bottom of the bolt about halfway up so that fluidwill flow from bore 29 into bore 2i and then up through groove 31 intoan annular space 33 which surrounds the bolt adjacent to the crystalmeans C.

Each of the bodies 11, 27 and 13 has the faces thereof which are incontact with the crystals 23 and 25 formed with a series of transverselyextending radial grooves 35,37,39 and at which extend from the innercircumferences at such ringlike members to their outer circumferences sothat air which has entered the annulus 33 flows radially outwardly incontact with all faces of the crystal elements.

While the preferred embodiment has been described, it is evident thatthe same type of construction is susceptible to modifications withoutdeparting from the principles of the invention. For example, instead ofsupplying the air through conduit ill, the upper portion of thetransducer can be surrounded by an enclosure to which air is suppliedfor flow from the outside of the transducer to the inside and then outthrough the longitudinal bore 29 and the conduit 31. It is also evidentthat the transducer 13 can be supported in any desired way whenoperating, as by suitable clamps or supporting discs which will permitvibration while maintaining the desired position. it is also evidentthat the radial grooves can be formed in the crystal elements ratherthan in the metal bodies.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

l claim:

l. in a fluid cooled ultrasonic transducer comprising a back body; afront body; piezo electric crystal means sandwiched between and incontact with end faces of said back body and said from body; and acentral bolt holding together said back body, said from body, and saidpiezo electric crystal means, the improvement wherein:

said transducer has duct means extending transversely from adjacent saidcentral bolt to the outside of said transducer between said front bodyand said crystal means, and between said back body and said crystalmeans, for conducting cooling fluid in contact with said crystal means;and

said central bolt has longitudinal passage means therein communicatingwith said duct means, said passage means being adapted to conductcooling fluid.

2. in an ultrasonic transducer in accordance with claim 1, said ductmeans comprising a plurality of transverse grooves formed in said endfaces of said front body and said back body, said bolt being spacedannularly from said piezo electric crystal means to form an annuluscommunicating with said transverse grooves, and said longitudinalpassage means in said bolt communicating with said annulus.

3. in an ultrasonic transducer in accordance with claim 2, saidlongitudinal passage means comprising a central passage in said bolt,and an external groove in said bolt extending from the end thereof tosaid annulus, said end of said bolt being located in a bore in saidfront body and terminating at a point spaced from the bottom of saidbore whereby fluid flows between said central passage and said bore andbetween said bore and said annulus.

d. in a fluid cooled ultrasonic transducer in accordance with claim 2wherein said piezo electric crystal means comprises a pair of crystalsand a spacer therebetween, said spacer having two opposite faces incontact with said crystals, the further improvement wherein: said twoopposite faces have transverse grooves therein extending from saidannulus adjacent said central bolt to the outside of said transducer forconducting cooling fluid in contact with said crystals. 5. in a fluidcooled ultrasonic transducer in accordance with claim l, the furtherimprovement of means coupled to said bolt for supplying a stream ofcooling fluid thereto.

a. in a fluid cooled ultrasonic transducer in accordance with claim 2wherein said back body, said front body and said piezo electric crystalmeans are all rings having an inner circumference and an outercircumference, the further improvement wherein said grooves extendradially from said inner circumference to said outer circumference ofsaid bodies.

i. in a fluid cooled ultrasonic transducer in accordance with claim 4,the further improvement wherein said back body, said cumference to saidouter circumference of said bodies and said spacer.

1. In a fluid cooled ultrasonic transducer comprising a back body; afront body; piezo electric crystal means sandwiched between and incontact with end faces of said back body and said front body; and acentral bolt holding together said back body, said front body, and saidpiezo electric crystal means, the improvement wherein: said transducerhas duct means extending transversely from adjacent said central bolt tothe outside of said transducer between said front body and said crystalmeans, and between said back body and said crystal means, for conductingcooling fluid in contact with said crystal means; and said central bolthas longitudinal passage means therein communicating with said ductmeans, said passage means being adapted to conduct cooling fluid.
 2. Inan ultrasonic transducer in accordance with claim 1, said duct meanscomprising a plurality of transverse grooves formed in said end faces ofsaid front body and said back body, said bolt being spaced annularlyfrom said piezo electric crystal means to form an annulus communicatingwith said transverse grooves, and said longitudinal passage means insaid bolt communicating with said annulus.
 3. In an ultrasonictransducer in accordance with claim 2, said longitudinal passage meanscomprising a central passage in said bolt, and an external groove insaid bolt extending from the end thereof to said annulus, said end ofsaid bolt being located in a bore in said front body and terminating ata point spaced from the bottom of said bore whereby fluid flows betweensaid central passage and said bore and between said bore and saidannulus.
 4. In a fluid cooled ultrasonic transducer in accordance withclaim 2 wherein said piezo electric crystal means comprises a pair ofcrystals and a spacer therebetween, said spacer having two oppoSitefaces in contact with said crystals, the further improvement wherein:said two opposite faces have transverse grooves therein extending fromsaid annulus adjacent said central bolt to the outside of saidtransducer for conducting cooling fluid in contact with said crystals.5. In a fluid cooled ultrasonic transducer in accordance with claim 1,the further improvement of means coupled to said bolt for supplying astream of cooling fluid thereto.
 6. In a fluid cooled ultrasonictransducer in accordance with claim 2 wherein said back body, said frontbody and said piezo electric crystal means are all rings having an innercircumference and an outer circumference, the further improvementwherein said grooves extend radially from said inner circumference tosaid outer circumference of said bodies.
 7. In a fluid cooled ultrasonictransducer in accordance with claim 4, the further improvement whereinsaid back body, said front body, said pair of crystals, and said spacerare all rings having inner and outer circumferences, the furtherimprovement wherein said grooves extend radially from said innercircumference to said outer circumference of said bodies and saidspacer.